One night in 1945, ten-year old Matt Stone awakes to find his mother and a drunken Army sergeant having sex. Believing the man is attacking his mother, Matt leaps on him. The sergeant throws him off then beats Matt’s mother, calling her a tramp. Matt grabs a nearby Japanese sword and stabs the man to death. Years later, Helen, Matt’s older and richer girlfriend, catches him having an affair with a belly dancer and they argue. When Helen calls the dancer a tramp, Matt mentally flashes back to that night in 1945, and strangles her to death. He places her corpse behind the steering wheel, puts the car in gear, and watches as it crashes into the lake. Days later, Ann Moy and her daughter, Tina, eat breakfast when Tina asks for lunch money. Ann tells Tina to take two dollars from her purse, but the girl takes three. She goes outside, and is almost run over by Matt. Tina jumps into Matt’s car and asks for a ride. After Matt accidently hits and kills a dog, a frantic Tina demands to be dropped off at a cemetery to visit her father’s grave. Across town, Ann’s friend, Julia Marstow, invites Ann to dinner to meet Clarence, a man Julia describes as “Burt Reynolds from the neck down.” Ann refuses, but Julia insists. Later, Ann is in her shop, changing a mannequin, when she slips and falls. Matt appears and catches her. After flirting with her, Matt gets into his car and finds a motel where he seduces the female clerk. Next, he goes to Clarence’s shop to collect some business cards that identify him as an investment manager. Julia arrives, sees Matt’s card, tells him she is interested in investing and invites him to dinner. That night at Julia’s mansion, Ann ignores Clarence, but makes a date with Matt. When Ann gets home, Tina is infuriated and accuses Ann of never loving her father. That Sunday, Matt takes Ann to the zoo, unaware that “Karate” Pete, a burly Asian man, is secretly watching them. When Ann gets home, Tina demonstrates her anger by “accidentally” breaking an antique plate. After weeks of courtship, Ann meets Matt at his motel, unaware her daughter is watching. Later, Ann takes Matt to meet Tina, but when she sees him, Tina runs away. Matt takes Ann to a cocktail lounge and convinces her to invest $10 thousand with him. However, he spots Pete, and later, Matt meets Pete in his room, where they discuss Matt’s previous stay in a mental institution and the other women he has killed. When Matt refuses to cut Pete into his newest swindle, Pete puts his fist through a nightstand, and Matt tells Pete of his plans to rob Julia’s mansion. The next night, Tina hides in the back of Matt’s car as he drives to a carwash. Once there, Matt rigs a pulley system to the roof. When Pete arrives, Matt drops a noose around the big man’s neck and hoists him into the air. Pete pulls a switchblade knife, cuts himself down, chases Matt into his car, and smashes out the driver’s window trying to get at him. Matt starts the car and runs Pete over, then to the motel, where Tina leaps out of the car and runs into the woods. Unable to catch her, Matt yells that he will kill her if she tells anyone. Tina runs home and calls the police, but is too frightened to talk. The next day, Matt takes Ann and Tina to the park, where Tina tells an unbelieving Ann about the murder. On the way home, Tina claims to be cold. She asks Matt to roll up his window, but is disappointed to find he has already repaired it. The next day, Ann attempts to convince Tina she is wrong about Matt, but ends up slapping her when she screams that she saw Matt and Ann having sex. Later, Matt goes to Julia’s home to talk business, but Julia insists her lawyer check into his company before she invests. Matt then meets with Ann and convinces her to invest $10 thousand. Meanwhile, Julia lays flowers on her three husband’s graves when Tina appears and tells her about Pete’s murder. Although Julia does not believe Tina, she invites Ann to come over for a talk. That night, Matt breaks into Julia’s house and forces her to open a wall safe. Julia pulls out a revolver, but Matt knocks it from her hand. She snatches an antique knife, but Matt grabs the knife and stabs her. He pulls down the drapes to wipe the blood from his hands and reveals Tina looking in through the window. He chases Tina into the cemetery where she hides in a chapel, but she gives away her position when she screams after seeing a corpse laid out for a wake. As Matt rushes in, Tina falls down a flight of stairs and knocks herself unconscious. Matt flashes back to his mother’s funeral and runs back to Julia’s, only to discover that there is nothing of value in the safe. Just then, Ann arrives, sees Julia's dead body and screams. Matt attempts to drown her by sticking her head into an aquarium, but Tina appears, takes a sword from a wall display and runs him through. As Matt dies, Ann grabs the hysterical Tina and they run from the house.